1. Field of Invention
The present invention relates to a liquid crystal display having a pair of substrates holding a liquid crystal layer and an electronic appliance including the liquid crystal display. More particularly, the present invention relates to the technology of obtaining a bright display with high contrast by providing both a transmissive display unit and a reflective display unit.
2. Description of Related Art
Currently, liquid crystal displays having small power consumption have been extensively used for a display unit in various kinds of electronic appliances, such as notebook personal computers, portable game machines and electronic notebooks. Particularly, in recent years, demand for a liquid crystal display capable of displaying color has increased as the display contents are diversified. In particular, the liquid crystal displays include the reflective structure type and the transmissive structure type according to the service applications.
A transmissive liquid crystal display has a structure with a backlight to improve visibility in dark places. However, with the transmissive liquid crystal displays the visibility is degraded in an environment in which external light brighter than the backlight is present, such as outdoors. Further, the power consumption is also high.
A reflective liquid crystal display has a display structure whereby external light is reflected by a reflector, and therefore, no backlight is required. This has the advantage of low power consumption, however, the visibility is degradable in dark places where the external light is weak.
A transflective liquid crystal display has been provided as a structure having both the advantages of a conventional transmissive liquid crystal display and a conventional reflective liquid crystal display. FIG. 17 shows an example of this kind of the conventional transflective liquid crystal display as disclosed in Japanese Unexamined Patent Application Publication No. 10-282488. In a basic structure of a transflective liquid crystal display A in this example, a liquid crystal layer 102 is held between upper and lower glass substrates 100 and 101, and a backlight unit 103 is provided outside the lower glass substrate 101. A plurality of reflectors 105 having a plurality of small holes 104 for light transmission are intermittently formed on an upper surface on the liquid crystal side of the lower glass substrate 101. A liquid crystal drive electrode 106 formed of a transparent conductive material is formed to cover most of the reflectors 105. A wiring pattern 107 and a TFT (thin film transistor element) 108 to drive each liquid crystal drive electrode 106 are formed on the substrate 101. A part of the reflectors 105 are extended onto the wiring pattern 107 and the TFT element 108 via an insulating film 110, and an alignment layer 111 is formed covering the reflectors 105 and the liquid crystal control electrodes 106. A color filter 113, an opposing electrode 114 and an alignment layer 115 are laminated on a surface on the liquid crystal layer 102 side of the upper glass substrate 100. In the structure shown in FIG. 18, a retardation film and a polarizer are appropriately disposed outside the glass substrates 100 and 101, however, they are omitted in FIG. 17.
In the transflective liquid crystal display A of the structure shown in FIG. 17, the light incident from the external side of the liquid crystal display is transmitted through the glass substrate 100, the color filter 113, the opposing electrode 114, the alignment layer 115, the liquid crystal layer 102, the alignment layer 111, and the liquid crystal drive electrode 106, and is reflected by the reflectors 105, and transmitted again through the liquid crystal drive electrode 106, the alignment layer 111, the liquid crystal layer 102, the alignment layer 115, the transparent electrode 114, the color filter 113, and the glass substrate 100, and reaches the naked eye of a viewing person. The color display can be achieved because the alignment-controlled liquid crystal layer 102 controls the transmissivity of the light reflected by the reflectors 105. The light generated by the backlight unit 103 is transmitted through the hole 104 for light transmission, and then, the liquid crystal drive electrode 106, the alignment layer 111, the liquid crystal layer 102, the alignment layer 115, the opposing electrode 114, the color filter 113 and the glass substrate 100, and reaches the naked eye of the viewing person, and the color display can be achieved because the alignment-controlled liquid crystal layer 102 controls the transmissivity of the light.
The transflective liquid crystal display A shown in FIG. 17 can realize the transmissive display making use of the transmitted light from the backlight 103 and the reflective display making use of the external light by one liquid crystal display.